Studies of the reactions of hydroxyl radicals. II

1966 ◽  
Vol 291 (1424) ◽  
pp. 85-93 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Carbon Monoxide ◽  
Hydroxyl Radicals ◽  
Room Temperature ◽  
Order Reaction ◽  
Methyl Radicals ◽  
Third Order ◽  
Experimental Conditions ◽  
Homogeneous Decomposition ◽  
Methane Carbon

The homogeneous decomposition of hydrogen peroxide has been used as a source of hydroxyl radicals. In part I values were reported for the relative rates of reaction of hydroxyl radicals with methane, carbon monoxide, formaldehyde and hydrogen peroxide. In this paper these values are confirmed for different experimental conditions and more consideration is given to details of subsequent reactions. The reaction of methyl radicals with oxygen has previously been shown to occur by a third order reaction both at 200 °C (Hoare & Walsh 1957) and at room temperature (Christie 1958). Present results show that the reaction is second order at 525 °C as suggested by Barnard & Honeyman (1964). In the absence of added oxygen, methyl radicals combine to give ethane which in turn reacts with hydroxyl radicals twelve times more rapidly than does methane.

Studies of the reactions of hydroxyl radicals. I

1966 ◽  
Vol 291 (1424) ◽  
pp. 73-84 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Carbon Monoxide ◽  
Kinetic Study ◽  
Hydroxyl Radicals ◽  
Rate Constants ◽  
The Other ◽  
General Applicability ◽  
Preliminary Account ◽  
Homogeneous Decomposition ◽  
Methane Carbon

This paper describes how the homogeneous decomposition of hydrogen peroxide vapour has been successfully used as a source of hydroxyl radicals in a kinetic study of the relative rates of reaction of hydroxyl radicals with methane, carbon monoxide, formaldehyde and hydrogen peroxide. It has been found that the method is of general applicability provided subsequent reactions of radicals formed can be controlled. With hydroxyl radicals so produced from the decomposition of hydrogen peroxide, surprisingly consistent values were obtained for the relative rates of reaction of methane and carbon monoxide with hydroxyl radicals. Thus, within an accuracy of 10%, the ratios of rate constants for reaction of hydroxyl radicals with methane and carbon monoxide were found to be 3.6 at 650 °C, 2.1 at 525 °C and 0.85 at 400 °C. The rates of reaction of hydroxyl radicals with formaldehyde and hydrogen peroxide were less accurately determined because of expected additional reactions. Within an accuracy of about 50% it was estimated that hydroxyl radicals reacted ten times as fast with hydrogen peroxide as with carbon monoxide at 525 °C. At the same temperature hydroxyl radicals reacted 33 ± 6 times as fast with formaldehyde as with methane. Data were obtainable at temperatures as low as 400 °C even though heterogeneous decomposition of hydrogen peroxide was relatively more important at these temperatures. This was because heterogeneous decomposition of hydrogen peroxide did not cause oxida­tion of the other gases which were also present. A preliminary account (Hoare 1962) of this work has previously been published.

The formation of O2(a1Δg) in homogeneous and heterogeneous atom recombination

1986 ◽  
Vol 64 (12) ◽  
pp. 1614-1620 ◽  
Author(s):  
A. A. Ali ◽  
E. A. Ogryzlo ◽  
Y. Q. Shen ◽  
P. T. Wassell
Keyword(s):  
Kinetic Study ◽  
Gas Phase ◽  
Molecular Oxygen ◽  
Rate Constant ◽  
Room Temperature ◽  
High Efficiency ◽  
Flow System ◽  
Order Reaction ◽  
Third Order ◽  
First Order

The recombination of oxygen atoms has been studied in a discharge flow system at room temperature. The yield of O2(a1Δg) in the recombination on Pyrex has been found to be 0.08 (±0.02). In the gas phase, O2(a) was found to be formed in a process that is second order in [O] and first order in [N2]. The rate constant for this third-order reaction was found to be 3.4 (±0.4) × 10−34 cm6∙molecule−2∙s−1, representing a yield of 0.07 (±0.02). In the presence of molecular oxygen, the rate of production of O2(a) was found to increase. A kinetic study of this effect led to the conclusion that collisions of molecular oxygen with an unidentified precursor can produce O2(a) with high efficiency.

scholarly journals Tailorable Aqueous-Media Synthesis of Heterogeneous Copper Nanoparticles Hybrids and Application in Selective Oxidation of Benzene

2019 ◽  
Author(s):  
Noelia Losada-Garcia ◽  
Alba Rodriguez-Otero ◽  
Jose M Palomo
Keyword(s):  
Hydrogen Peroxide ◽  
Selective Oxidation ◽  
Copper Nanoparticles ◽  
Room Temperature ◽  
Aqueous Media ◽  
Green Technology ◽  
Direct Oxidation ◽  
Experimental Conditions ◽  
Copper Species ◽  
Oxidation Of Benzene

Novel heterogeneous nanocatalysts has been synthesized in aqueous media at multimilligram scale for highly selective direct oxidation of benzene to phenol in aqueous media. The synthesis of a novel biohybrids containing copper nanoparticles (CuNPs) by an efficient and green technology have been described. The methodology involves the combination of an enzyme and a copper salt in aqueous media at room temperature. It was possible to control the copper species and nanoparticle size depending on the experimental conditions, e.g. pH, reducing step, amount of enzyme, obtaining novel heterogeneous nanobiohybrids containing exclusively Cu (0)NPs, Cu2O (Cu(i)) NPs or very crystalline Cu3(PO4)2 (Cu (ii)) NPs. Very small dispersed copper nanoparticles were formed in all cases (from 3 to 15 nm). These novel CuNPs biohybrids were evaluated as catalyst in the selective oxidation of benzene to phenol in water at 30ºC using hydrogen peroxide as oxidant, obtaining excellent yields and selectivity of phenol (>80% yield, >95% selectivity). <br>

Primary process(es) in the mercury-photosensitized decomposition of dimethyl ether at 2537 Å

1968 ◽  
Vol 46 (16) ◽  
pp. 2693-2697 ◽  
Author(s):  
R. Payette ◽  
M. Bertrand ◽  
Y. Rousseau
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Light Intensity ◽  
Dimethyl Ether ◽  
Molecular Hydrogen ◽  
Room Temperature ◽  
Primary Process ◽  
Methyl Radicals ◽  
Hydrogen Atoms ◽  
Radical Recombination

The mercury-photosensitized decomposition of dimethyl ether has been studied at room temperature and at pressures ranging from 10 to 200 Torr.The formation of an excited dimethyl ether (DME) molecule has been verified by following the rates of formation of methane, ethane, and carbon monoxide with various ether pressures.The study of the variation of the quantum yield of molecular hydrogen formation with absorbed light intensity at high ether pressures has shown that the primary process involves the dissociation of ether molecules into hydrogen atoms and methoxy methyl radicals:[Formula: see text]The results presented in this paper indicate that the excited DME molecule can originate in a radical recombination between hydrogen atoms and methoxy methyl radicals.

scholarly journals The high-temperature oxidation of propane

1959 ◽  
Vol 250 (1263) ◽  
pp. 493-513 ◽  
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidation Products ◽  
Methyl Radicals ◽  
Secondary Oxidation ◽  
Chain Reaction ◽  
Radical Chain ◽  
Temperature Oxidation ◽  
Second Stage ◽  
Reaction Proceeds ◽  
Homogeneous Decomposition

Above 400 °C propane is oxidized by a two-stage degenerately branching chain reaction. The first 20% of reaction proceeds by an HO 2 /C 3 H 7 radical chain where the main immediate products are propylene and hydrogen peroxide. Pyrolysis of a small fraction of the propyl radicals gives rise to methyl radicals and finally formaldehyde. The further oxidation of formaldehyde by molecular oxygen probably accounts for the observed chain branching although at temperatures above 475 °C homogeneous decomposition of hydrogen peroxide may lead to the initiation of new chains. In the second stage of the reaction the secondary oxidation of propylene becomes important. While propane still in the main reacts to form propylene the subsequent oxidation of the propylene alters both the kinetics and the oxidation products so that the reaction appears overall to proceed by a mechanism similar to that operative at temperatures below 400 °C where the important branching agents are probably higher aldehydes.

An ESR study of irradiated mixtures of hydrogen peroxide and Cu(II) complexes at 77 K

1988 ◽  
Vol 53 (12) ◽  
pp. 3080-3088 ◽  
Author(s):  
Pavel Stopka
Keyword(s):  
Hydrogen Peroxide ◽  
High Pressure ◽  
Catalytic Activity ◽  
Oxalic Acid ◽  
Hydroxyl Radicals ◽  
Room Temperature ◽  
Active Species ◽  
Mercury Lamp ◽  
Catalytically Active ◽  
High Concentrations

When aqueous solutions containing hydrogen peroxide and CuSO4 are irradiated by a high-pressure mercury lamp at room temperature and at 77 K, hydrogen peroxide decomposes and hydroxyl radicals generated in high concentrations coordinate to CuSO4. The catalytic activity of Cu(II), which depends on the choice of the ligand (triene, diene, ethylenediamine, ammonia, EDTA, oxalic acid and glycerine) and the proportion between the monomeric and dimeric forms of the Cu(II) complex, shows a maximum at a concentration of 10-4 mol dm-3. The catalytically active species is the monomeric Cu(II) complex, the dimer being inactive.

scholarly journals Tailorable Aqueous-Media Synthesis of Heterogeneous Copper Nanoparticles Hybrids and Application in Selective Oxidation of Benzene

2019 ◽  
Author(s):  
Noelia Losada-Garcia ◽  
Alba Rodriguez-Otero ◽  
Jose M Palomo
Keyword(s):  
Hydrogen Peroxide ◽  
Selective Oxidation ◽  
Copper Nanoparticles ◽  
Room Temperature ◽  
Aqueous Media ◽  
Green Technology ◽  
Direct Oxidation ◽  
Experimental Conditions ◽  
Copper Species ◽  
Oxidation Of Benzene

Novel heterogeneous nanocatalysts has been synthesized in aqueous media at multimilligram scale for highly selective direct oxidation of benzene to phenol in aqueous media. The synthesis of a novel biohybrids containing copper nanoparticles (CuNPs) by an efficient and green technology have been described. The methodology involves the combination of an enzyme and a copper salt in aqueous media at room temperature. It was possible to control the copper species and nanoparticle size depending on the experimental conditions, e.g. pH, reducing step, amount of enzyme, obtaining novel heterogeneous nanobiohybrids containing exclusively Cu (0)NPs, Cu2O (Cu(i)) NPs or very crystalline Cu3(PO4)2 (Cu (ii)) NPs. Very small dispersed copper nanoparticles were formed in all cases (from 3 to 15 nm). These novel CuNPs biohybrids were evaluated as catalyst in the selective oxidation of benzene to phenol in water at 30ºC using hydrogen peroxide as oxidant, obtaining excellent yields and selectivity of phenol (>80% yield, >95% selectivity). <br>

Sign in / Sign up

Export Citation Format

Share Document